The Overproof showing is underlain by subaerial, massive and amygdaloidal basalt flows of the Vancouver Group, Upper Triassic Karmutsen Formation, which have undergone low grade greenschist regional metamorphism. Interbeds of black argillites and limestone occur at lower elevations within the Karmutsen Formation. A sedimentary succession of limestone and argillite of the Triassic to Jurassic Kunga Group occur as down dropped blocks underlying the southern portions of the property. Submarine pillow and massive basalts lie north of the area. Rhyolite dikes and flow banded sheets intrude the rocks.

Several north trending quartz veins, associated with dikes and faults, carry gold mineralization with disseminated and fracture filled pyrite and minor arsenopyrite. Common alteration includes silicification, chloritization, epidotization, hematization, and tourmaline.

A quartz vein cutting massive grey limestone of the Upper Triassic Sadler Formation (Kunga Group) assayed 44.6 grams per tonne gold (Assessment Report 9830) and thin quartz veinlets cutting limestone with interbedded argillite assayed 13.2 grams per tonne gold (Assessment Report 8405).